Cellular telephones are often used in automobiles.
A cellular telephone can be used in a car kit. The car kit holds the telephone and has connections to provide power to the cellular telephone. The car kit often operates in hands-free mode, so that the call is carried out in speakerphone mode.
The car kit can be placed up high, above the chassis of the automobile. This puts the cell phone closer to the glass and allows better reception. However, this location can be less aesthetically pleasing.
A less-intrusive mounting places the cell phone down lowerxe2x80x94below the auto chassis, e.g. in an arm rest. Reception would often be impaired at this location because of interference from the chassis of the automobile. Therefore, this type of mounting can include a connection to an external antenna.
This external antenna can provide additional gain for the cellular transmission and reception, e.g. 6 dbi of gain.
The user often wants to conduct a private conversation. Therefore, the user may remove the handset from the car kit for a private conversation in the vehicle. The handset""s connection to the external antenna is lost when the phone is removed from its cradle. For a short time, until the phone is brought up to the user""s ear, the shielding of the vehicle cab could shield the signal and reduce the signal strength. This could cause the call to be dropped.
The present system uses an in-vehicle passive antenna, within the car kit, to connect signal to the external antenna when the portable phone is not resting within the kit.
The in-vehicle antenna is passive in the sense that it couples RF transmissions and receptions to and from the cell phone when the handset is not docked. Therefore, when the cell phone is removed from the car kit, the connection to the external antenna can still assist handset transmission and reception. The passive connection is the effective when the cell phone antenna is closest to the car kit, e.g. when the cell phone is being docked and undocked.
According to a disclosed mode, an electronic or mechanical switch switches the connection between electrical connection to the external antenna and passive connection to the external antenna, depending on whether the cell phone is connected or removed.